tighten transport failure semantics

main/trikke_sensor_main.c

@@ -168,6 +168,7 @@ static void write_binary_packet_until_sent(
     size_t packet_size)
 {
     while (true) {
+        const bool was_pending = sender->pending;
         const trikke_transport_status_t status =
             trikke_transport_sender_step(
                 sender, &context->transport, packet, packet_size);
@@ -175,12 +176,20 @@ static void write_binary_packet_until_sent(
             return;
         }
         if (status == TRIKKE_TRANSPORT_FATAL) {
-            // Preserve the in-flight packet and stop consuming the queue. A
-            // fatal backend invariant is not safely recoverable or retryable.
+            // The binary stream is terminal at this point, so a final text
+            // diagnostic cannot corrupt later frames. Preserve the packet and
+            // stop consuming the sample queue.
+            esp_log_level_set(TAG, ESP_LOG_ERROR);
+            ESP_LOGE(TAG, "fatal transport invariant; output task suspended");
             while (true) {
-                vTaskDelay(portMAX_DELAY);
+                vTaskSuspend(NULL);
             }
         }
+        if (status == TRIKKE_TRANSPORT_PENDING && !was_pending) {
+            // Poll once immediately after acceptance. Subsequent pending polls
+            // are paced so a future nonblocking backend cannot busy-spin.
+            continue;
+        }
         vTaskDelay(pdMS_TO_TICKS(TRIKKE_TRANSPORT_RETRY_DELAY_MS));
     }
 }
@@ -349,11 +358,11 @@ void app_main(void)
     s_context.sample_queue =
         xQueueCreate(TRIKKE_SAMPLE_QUEUE_DEPTH, sizeof(trikke_wire_sample_t));
     if (s_context.sample_queue == NULL) {
+        trikke_usb_transport_deinit(&s_context.usb_transport);
         ESP_LOGE(TAG, "sample queue allocation failed");
         l3g4200d_deinit(&s_context.gyroscope);
         adxl345_deinit(&s_context.accelerometer);
         i2c_del_master_bus(bus);
-        trikke_usb_transport_deinit(&s_context.usb_transport);
         return;
     }
 
@@ -370,11 +379,11 @@ void app_main(void)
             vTaskDelete(acquisition_task_handle);
         }
         vQueueDelete(s_context.sample_queue);
+        trikke_usb_transport_deinit(&s_context.usb_transport);
         ESP_LOGE(TAG, "telemetry task creation failed");
         l3g4200d_deinit(&s_context.gyroscope);
         adxl345_deinit(&s_context.accelerometer);
         i2c_del_master_bus(bus);
-        trikke_usb_transport_deinit(&s_context.usb_transport);
         return;
     }